1. Field of the Invention
The present invention generally relates to oil and gas pipelines and, more particularly, is concerned with a pipeline buoyancy control assembly and a tie-down attachment member therefor.
2. Description of the Prior Art
Oil and gas pipelines often need to be anchored or stabilized. Underwater pipelines and pipelines buried in saturated soils may attempt to float. This buoyancy must be controlled by some means. A variety of assemblies or methods have been developed over the years for anchoring pipelines. Passive gravity systems, such as weights, are common. Other systems have included the employment of helical screw anchors with steel or polyester pipebands.
A representative example of a prior art pipeline anchor apparatus is disclosed in U.S. Pat. No. 5,730,552 to Johannesson et al. The Johannesson patent shows an elongated flexible tie-down strap extending over a pipeline and attached at opposite ends to left and right anchor units. The tie-down strap is made of polyester webbing and has a loop formed and sewn at each of its opposite ends of the strap. Each loop is secured to a tie-down bracket along a side thereof facing the pipeline. The tie-down brackets are mounted to extension rods which, in turn, are attached to anchor rods of the respective anchor units. Each anchor rod has a helical anchor attached thereabout. Each tie-down bracket has a side sleeve-like connector defining a channel or slot running alongside the bracket through which passes one of the tie-down strap loops. Each loop of the tie-down strap wraps around an outer wall of the side connector of one of the tie-down brackets.
Problems exist, however, with many prior art designs. For instance, in the case of the Johnannesson et al. anchor apparatus, eccentric loading due to the strap being connected by the tie-down bracket on one side of the anchor rod creates undesirable high bending stress and concentration of stress in the anchor rods of the arrangement. Further, due to corrosion, the side connector of the tie-down bracket may break at either of its locations of securement to the anchor rod and thereby permit release of the strap. If this occurs, the pipeline would be free to float upwardly at that point overloading adjacent anchor sets, which could lead to a catastrophic failure.
Consequently, a need remains for an assembly which provides a solution to the aforementioned problems in the prior art without introducing any new problems in place thereof.